The present invention relates to the arm used to carry a magnetic head in a magnetic disk drive unit. In particular, the invention relates to a method of removing a ball stake (or swage) mounted magnetic head from the support arm.
There has been a continual drive to increase the storage density in magnetic disk drive units. This has been achieved in part by stacking magnetic disks in a "pack" all carried within the same disk drive unit. Each side of each disk has its own associated magnetic head used for reading and writing information thereon. Each magnetic head has its own associated support arm which positions the head above the disk surface. By moving the arm, the magnetic head is moved between tracks on the disk surface. A servomotor is connected to the opposite end of the support arm. The magnetic head is moved between tracks by activating the servomotor whereby the support arm pivots and the magnetic head at the opposite tip of the arm is swung between adjacent tracks on the disk surface. A linear actuator may alternatively be used to move a magnetic head. A linear actuator moves the head inward or outward on the disk along a straight line.
To further increase space savings in the disk drive unit, a single servomotor typically controls all of the support arms and their associated magnetic heads. Thus, all of the support arms are connected together and pivot about the same pivot point. This configuration is identified as an "E-block" (which refers to the shape formed by the adjacent arms and the servomotor/pivot assembly).
Each magnetic head is connected to the support arm using a mounting method known as "ball staking" or "swaging". In ball staking two pieces, a hole in one piece is aligned with a hollow tube which extends from a second piece. A rounded shape (the "ball") is forced through the hollow tube which causes the tube metal to expand and lock the two pieces together.
A problem associated with past ball stake mount designs is that there was no economical method to remove a single defective magnetic head from the assembly. Once ball stake mounted, the support structure was very difficult to disassemble and was easily damaged. Thus, the entire E-block assembly typically had to be replaced if a single magnetic head malfunctioned.
One attempt to overcome the problems associated with past ball stake mount designs was disclosed in Toensing, U.S. Pat. No. 5,012,367 which has been assigned to Seagate Technology, Inc., the assignee of the present application. Toensing disclosed a removable ball staked head gimbal assembly as well as a method and apparatus of removing the assembly. In the assembly disclosed in Toensing, a bevel was provided between the ball staked support arm and magnetic head carrying arm. A removal tool is then inserted into the bevel so that the ball staked pieces are pried apart. The bevel is preferably provided by a mounting plate which is mounted to one of the arms. Ball staking occurs through the method described above.
In some instances, the deswaging operation causes the support arm to be bent during the removal process. If a single support arm of an E-block assembly is bent, the entire E-block assembly must be scrapped, increasing both the labor and the material costs of repair. Removal of the ball staked assembly may also result in damage to the magnetic head supporting arm. Often times, this makes it impossible to perform a failure analysis on the defective magnetic head assembly.